Math/Chemistry
posted by Chaney .
the atomic mass of an element is the mass, in grams, of one mole (mol), or 6.02 * 10^23.
A.) How many atoms are there in 3.5 mol od carbon?
B.) If you know that 3.5 mol of carbon weighs 42 grams, what is the atomic mass?
C.)Using you answer from (B), find the approximate mass of one atom of carbon

(6.02E23 atoms/1 mol) x (3.5 mols) = ??
Note how the mol unit in the numerator cancels with the mol unit in the denominator to leave atoms which is the unit you want to leave.
If 42 grams contains 3.5 mol, how many grams is in 1 mol? Wouldn't that be 42/3.5? (It's the old apple weight problem. If 10 apples have a mass of 5 pounds how much does each apple weigh? That is 5 pounds/10 apples = 0.5 pound each.)
Now you do the mass of 1 C atom just as in the apple problem. You know the mass of 6.02E23 atoms. 
Thanks for the help, This was a 8th grade question by the way.